Have I found My true friends?

Well, lately this question has been lingering in my head. When will I be absoulutely positive that I know who my true friends are. I thought before, that I had found that special friend. But then I also soon found out that she would be the same one to turn right back around and stab me in the back. The scenarsio is the same each time. You find a girl, talk talk talk, tell her your deepest thoughts,and then youre best friends. And then two months later , the same chick you thought had your back is using a knife to stab you in it. So i guess its true, friends do come and go. But I also thought it was true that you always have at least one genuine one to keep your sanity in the bunch. And I may have found my one, but how am I sure when all the others who I was almost positive about. Turned on me, and left me standing. Dont get me wrong, I love my best friend beyond words. I would give my last dying breath for her because I love her that much. But how do I know she will do the same for me.? Am I supposed to go with my heart, or my mind? haha. And this sounds a lot like a relationship type thing, but I assure you, I dont roll the opposite of normal, Im straight. But I do have a genuine love for my friends. And with that said, I want to know for sure if the ones that I have are truly there for me, as I am there for them. Im genuine with it, so how do I know positively that they are genuine with it too.

The four people in this pic, including myself, used to be best friends. But then, the two who have been marked out kind of strayed onto other things leaving the two remaining with nothing but each other....which leads to the pic you see below.

This girl here, truly is and hopefully will always be my bestfried. I know that we go through our ups and down, but we always overcome it all. and I am hoping that she truly is my real best friend. I believe this relationship to be genuine. and hopefully I am correct in my predictions. ;)